Aerial Effect

the undesirable radiation or reception of electromagnetic waves by electrical current conductors that are not intended to radiate or receive waves. The aerial effect occurs most often in the high-frequency energy transmission lines connecting a radio transmitter or receiver with an antenna. In radio installations the aerial effect causes distortion of the antenna’s directivity pattern, a reduction in the efficiency of high-frequency transmission lines, and so on. In a dual-conductor transmission line the aerial effect takes place because the symmetry is disturbed by the position of the conductors relative to surrounding objects or because there is equipment connected to the.line; in a coaxial cable it occurs because of a disturbance from contact between the external jacket and a ground or an apparatus housing; in a wave guide it takes place because gaps occur at the joints of individual sections of the wave guide; and so on. In a loop antenna the aerial effect is known as directivity pattern distortion and occurs when there is an imbalance in the symmetry of the construction of the loop itself or of the connecting conductors and adjacent apparatus, which causes the appearance of undesirable reception in a direction perpendicular to the plane of the loop.